Automatic common-battery party-line telephone system.



T. G. MARTIN. COMMUN BATTERY PARTY UNE TELEPHONE SYSTEM AUTOMT APPLICATDN FILED HB. 3, 1905.

4 SHEElS-SHEE Y.

G. MARTIN. Mmm/TTT@ TrYTMMoN BATTERY PARTY UNE TELEPHUNE SYSTEM, APFUUAHON FILED FEB` 3, 130.

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T. G. MARTIN AUTGMATLC CUNIMON BATTERY PARTY LINE TELEPHONE SYSTEM, APPUCAUUN mw rm 3. wos

4 SHEETS-SHEU 3.

I. G. MARUN. ANUMAN@ COMMON BAUEN PARTY LINE TELE PHONE SYSTEM,

APPLICATON FILED H1B. 34 1906.

Raga/Q C( [/Vul/r/af/M UNITED STATES PATENT OFFICE.

TALBOT G. MARTIN, F CHICAGO, ILLINOIS, ASSIGNOB., BY MFSNE ASSIGNMENTS, T0 FIRST TRUST ANI) SAVINGS BANK, TRUSTEE, OF CHICAGO, ILLINOIS.

Specication of Letters Patent.

Patented Aug. 24, 1915.

Application led February 3, 1906. Serial No. 299,268.

To all whom it may concern Be it known that I, Tamar G. MARTIN, a. citizen of the United States of America, and resident of Chicago, Cook county= Illinois,

s have invented u certain new and useful Improvement in Automatic Common-Battery Par v,'-Line Telephone Systems, of which the following is a. specification.

My invention relates to automatic or semiautomatic telephone systems in general, but more particularly to systems in which the subscribers are provided with switch devices for sending the electrical impulses necessary for operating the electrically-propelled and step-by-stepactuated trunk-selecting and line-connecting switching machinery at the exchange or central station, and especially to telephone systems in which one or more of the subscribers lines are used as partylines.

In certain respects my invention is in the nature of an improvement on the party-line telephone system in my prior application No. 289,048 filed by me in the United States Patent Oice on the 25th day of November, 1905, and in which applica tion I have set forth an automatic party-line telephone system employing local batteries for charging `or operating the microphone transmitters at the subscribers stations.

Generally stated, therefore, the object of my present invention is the provision of an improved and highly eicient automatic party-line telephone system of the foregoing general character.

Special objects of my invention are the provision of an improved construction and arrangement whereby the features of my said prior invention mav be combined with and adapted for usel in conjunction with a common battery or centralized source of talking current; and the provision of certain details and features of improvement- :md novel combinations, all tending to increase the general eiciency and serviceability of a telephone system of this particular character.

To the foregoing and other useful ends.

my invention consists in matters hereinafter described and claimed.

In the accompanying drawings Figure 1 is a diagrammatic representation of two connected party-lines in an automatic telephonejsystem the principles of my invention. One of said lines is provided with two substations numbered 320 and 220, respectively-which are bridged between the line-conductorsthe other line being similarly equipped with substations 130 and -2.30, respectively. In said figure the sub-station. #320 is represented as calling the substation #130 through :i calling 51st-selector A, a connector C, and the irsbselector A. of the culled line. Since all of the sub-stations are identical, and since they are all similarly represented, it will be sullicient to describe only one. Fig. 2 is a diagrammatic perspective view showing the approximate relative positions of the parts of the firstselector A, the switch-frame of which is not shown. Fig. 3 is a similar view of the con.- nector. 65. Fig. 4 is a view similar to F ig. 1, ln which the subscriber at, sub-station #320 has called the subscriber at sub-station #120 on the same line where a third sub-station .fi-220 is bridged across the line between the former two.

All of the sub-stations are provided with the usual details essential to automatic substations of the class in question. Sub-station #320, for instance, is provided with a receiver 2 and a, switch-hook 3 which has radiating from its body a number of camarms 4, 5, 6 and 7. Said hook is suitably pirated on the so-called sub-station keyboard-frame which' carries most of the mechanical details of the telephone. As usual, the switch-hook is raised or1V lowered whenever the receiver is removed or restored to its place. The said hook is raised or lowered to accomplish certain switching opera.- tions to be disclosed, and for .controlling certain mechanical details that will be hereinafter described. Furthermore, saidsubstation has a transmitter 8, a ringer Y9, Vand an induction-coilIO with primary and secondary windings l1 and 12, respectively; also a couple of condensers 13 and I4, a signaling device composed of a push-button 15, a spring 16, and two ntact-points 17 and 18 whereby one side of the main line may be grounded; and in addition a relay 19 under the control of which are found the springs so, 21,22 and 23. when the 'swucuhwk is down the cam-arm 5 is held in contact ,with the spring 24, whereby said spring is tained at such time in a downwardly-fixed condition. Said spring and cam-arm are, therefore, normally in contact, and in this way a circuit is completed from the line through the ringer 9, which circuit includes, besides the said ringer 9, the ringer-circunspring 24 and condenser 13.

Asociated with the ringer-circuit-spng a 24 are two sets of springs 26 and 27, and 28 and 29. The members of each of these sets, whenV left to their own tension-that is, when the switch-hook is 11p-engage in contact with each other; the springs 26 and 27 g being in contact, and the springs 2S and 29 being in contact; and whenever the switchhook depresses the spring 24 the latter permits the springs 27 and 29, respectively, to separate from the Springs 26 and 2S. The cam-arxn 7 controls the springs 30, 31, 32 and 33 of which the members 30, 31 and 32 are retained out of engagement with each other, and the spring 32 in contact with the fourthsprlng 33; but when the switch'hook 2o is up the first three springs are forced together by the said cam-arm 7. Furthermore, while the switclrhoos is down the springs 34 and 35 are kept apart by the cam-arm 6, but when it rises the said springs Hex into contact. There are three other springs 36, 37 and 38 under the control of the cam-arm 4, which springs are known as the release-springs, and are forced into engagementhy the said cam-arm when the 3o latter engages a latemlly-projecting piece 39 at the upper extremity of the spring 38. However, when the switch-hook nears its lowermost position said arm disengages -om said spring and permits the said release-springs to again disengage. The calling device comprisestwo push-buttons 40 and 41, two springs 42 and 43, two contact points 44 and 45 and a so-called groundpost 46. against which Vthe springs 42 and 43 may be preed to ground either or both sides of the main line. The sub-station relay 19 is suitably mounted upon the keyboard or switch-frame relay is provided with an amature 47 by means of which, when the relay is magnetized. the springs 20 and 22, respectively. are separated from the springs 21 and 23. Furthermore, said relay has on its under side an armature locking devioe-'th'at'consists preferably of a metal 50 `piece-1S which, normally, is verticalh7 disposed and which is riveted to a spring 49 that is fastened to the rear of the relay The -ont end of said metal piece is bent at a right angle horizontally and to the front; and whenever the armature 47 is attracted by the magnet the tension in the spring 49 forces the metal member upward until the angled section rises in front of the armature 47. locking the latter in its at- 50 position; The switch-hook also carries'aslim link-rod 50 that passes through a guidelhole in a piece suitably secured near the front part of the relay. The lower end Vof said link works in front of the armature 5 47 and is bent at a right angle horizontally VIM and in a plane parallel to the plane of the armature. When the switch-hook is depressed the said link 50 descends far enough to drive the lock 48 below the edge of the armature 47, which latter then, if the mag- 7o net is not energized, resumes its normal position as shown at sub-station #320, Fig. 1. When the said armature is restored the relay-springs 20, 21, 22 and 23, of course, recnnage. In Fig. 2, the first-selector A. is shownwith the bank 75 of trunk-line-terminals beneath said selector, while the private-bank is located just above the trunk-line bank. The switch-shaft 7T is vertically disposed on 80 the front of the switch-frame and is retained connected therewith by bearings which are not shown. The shaft may be moved longitudinally in said bearings, and then rotatively, by ratchet and pawl electro-magnetically-operated devices, the vertical or longitudnal movements occurring first. Among the functions of the shaft an important one is that of holding the line-wipers 78 and 79 and the private-wiper 80. The first two comprise a set distinct from the latter, but both sets are located within range of the contacts of their respective banks 75 and 76. Said wipers are not only insulated from the shaft, but from each other as well. Among the details that are associated with the shaft' is a cam piece 81 which is of a. split sleeve design and secured to the shaft by a screw S2. The general shape of said cam, in crosssection, is that of an ova-l with the smaller end thereof on the side farthest away from the said screw. Said cam abuts on a hub 83 which is shrunk to the shaft near the middle of the latter. This hub carries a set of longitudinal teeth 84 that serve, as will bedis- 105 closed, to enable the forward rotation of the shaft, and as a means of locking the same against backward rotation. On the neck portion of said hub there is formed a set of circular teeth 85 that serve in turn as a 11 means b v which the raising 0f the shaft is accomplished, and for locking it. when raised. These circular teeth are traversed b v a. groove 86 into which the end of a so called shaft-rest 87 normally projects; but 11 when the shaft is rotated, any one of the said circular teeth which may be at the proper height slides onto the end of said rest. The end of said rest is, 0f course. adapted to fit circular grooves between said 12 circular teeth. The upper surface of the engaging end of the rest is level, but the under side is chamfered to form a bevel that corresponds to the upper slope of the circular teeth. 1 Above the hub 83 the shaft carries an arm 88 known as the normal-postarm, which, while the switch-shaft is at rest and while the shaft-rest occupies the slot S6, is retained against the normaLpost 89 by the 13 coil-spring 90, Said arm S8 exercises control over the so-called shaft-springs 91 and 92, so that when the shaft is raised said springs, which are normally separated, are permitted to come intocontact. A mong the magnets allotted to the rst-selector some are used as relays and others as operating magnets. The magnets 93 and 94 are among the former kind and are known, respectively, as the vertical and rotary line-relays. Said relays, by means of their ive armatures 95 and 96, control the springs 97 and 9S with respect to the ground-spring 99. All of said sprin are comprised in energizing circuits o operating magnets that operate the shaft. The magnet 100, armature 101 and sprinvs 102, 103 and 104 constitute the socaled bridge-cut-o-relay. The magnet 105, with its armature 106 and springs 107 and 108, constitutes the backrelease-relay, and is used for restoring the switch after the latter has seized a trunkline and when such release is desired. Of the operating magnets the magnet 109 is known as the vertical-magnet, and has allotted to it a so-called vertical-armature 110 supported by pivots 111 beneath said vertical-magnet. Whenever the coils 112 and 113 of said magnet become energized l' the armature 110 is attracted, and when the magnetism ceases the retracting-spring 114 restores said armature to its normal position. The upward movement ofthe armature. is limited by the pole-pieces of the magnet-coils 112 and 113, andthe lower limit 1s marked by a section of the switch-frame that passes under the arm 115. Said arm is known as the vertical-arm and extends forwardly yfrom the vertical-armature 110, of which latter it is a part. The verticalarm carries on its end a so-called verticalpawl 116 which, when the vertical-amature is attracted, engages with some one o the circular teeth 85 to raise the shaft. Normally, the under surface of the upper seetion of said pawl rests afggst a iece that is secured to the switche an that retains the pawl away from the circular teeth. When the vertical-armature is attracted, as the pawl rises, a retracting-spring 117 thrusts the upper side of the pawl towardthe circular teeth 85. As soon as said pawl clears its normal-rest, and by the time that the vertical-armature strikes the pole-pieces, the vertical-paw! strikes, with the rear surface of its upper section, a bumper piece which constitutes a part of the switch-frame.

c Therefore. the shaft is prevented from being raised unduly by its own momentumthat is, more than one notch at a time. It is clear, then, that :the pawl 116 not only raises the shafg'but that it also acts as a look at theend of each stroke. The verticalarm has also an L-shaped piece 118 on its under 'edge that engages a so-called releaselink 119 of flexible spring material. Said link carries an aperture 120 on its front end, and is secured to the armature 121 of one of the operative magnets 122, known as the release-magnet. Said amature is suspended from the frame by the supports 123, and is normally retained by the spring 124 away from the pole-piece-of the release-magnet. A stop is' suitably provided behind sai armature to limit its movements when retracted. The first-selector is provided with a peculiarly shaped device 125 known as the double-dog which is pivoted so that it may swivel about a vertical axis that passes through the -rzlvots 126. 0n its front side said double-dog divides into two dogs 127 and 12S, so situated and'constructed that the dog 127 may operate in conjunction with the circular teeth 85` while=the switch-shaft is raised and in normal rotary position, and so that the dog 12S may lookin ly engage the longitudinal teeth 84 when t e shaft is rotated. To the right of the pivots 126 the body of the double-dog extends rearwardly,

and projecting down therefrom is an arm L 129 that comes into play very prominently during the releasing of the switch. Near the extremityA and on the upper side thereof the body of the double-dog has a pin or lug that projects upwardly. Said lug is normally caught in the aperture 120 of the release-link 119, and then because of the tension in the spring 124 the dogs 127 and 12.8 areretained away from the shaft. Each time the vertical-ma et 109 is energized, it operates the shaft` ongitudinally-one step by means o the armaturelll. At the first step ofthelvertical-armature, the link 119 is drawn away from the lug 130 by the piece 118, and then the double-dog 1s rotated by. the retracting-spring 131, so that the`dogv12`falls under the first circular tooth, and so that when the vertical-armature returns to its normal position the said shaft will he retained by said dog in its new position. The release-link 119, while the double-dog-is free, rests with its endupon the lug 130, but out of locking engagement therewlth. When the vertical-armature is attracted a second time, the shaft is raised a second step, and the dog 12T at the second stroke passes from under the first tooth to a position4 under the secondY tooth holding the shaft aga-imas before.

The release-magnet 122 is composed of two coils, like the Yvertical-magnet 109, but. for convenience of illustration, only one. coil is shown. If, while the shaft is raised, the said release-magnet should be energized the release-armatnre "121' is attracted and the release-link 119 is thrust forward to catch the. lng 130 in the aperture 120. Upon the denergization otftherelease-magnet the retracting-spring 124 then withdraws the dogs 12'? and 128 from engagement with the 1 shaft-teeth, and the shaft being thus deprived of its temporary support falls to normal position by its own weight. After the shaft is once raised it may be rotated by a second operating magnet 132 known as the rotary-magnet- Said magnet has two coils 133 and 134 and, unlike the vertical-magnet, has its armature 135 pivoted in a. vertical plane. Said armature may be moved about a vertical axis that passes through the pivots 136 The limit of the movement of said armatureitoward the rotary-magnet is determined by the pole-pieces of said magnet, which movement is produced by the rotarymaguet itself. The motion of the armature in the opposite direction is produced by the letricring-spring 137, and is limited by a stop piece (not shown) behind the so-called rotary-arm 13S. This arm,.like the verticalarm, carries a so-called rotary-pawl 139. Said rotary-pawl normally rests against a stop that retains it away from the ongitudinal teeth, and when the rotary-armature is attracted it is drawn into engagement with the longitudinal teeth bya spring 140 attached to the rotary-arm by one end and to the rear of said pawl by the other. By the time that the rotary-armature strikes the pole-'pieces oi; the Vrotax:y-maguet, the rotary-paid also strikes a. bumping post, as does the vertical-pawl, and locks the shaft against further advance by the force of its own momentum. Atthe end of the Elst rotary step the dog 128 falls behind the first longitudinal tooth, so that when the rotarypawl falls back the shaft is retained. It should be evident that as the shaft is rotated the vertical-dog 127 is extricated from the groove of the Acircular tooth below which it fhasbeenrestingbythepassageoftherotary-dog 12S acres the longitudinal tooth over which it has to slide at the time; but at the of the rotation the tooth has been caught by the vertical-dog slides onto the shaft-rest S7, and the shaft is thus provided with 'a new support in lieu of the vertical-dog 12T and is still held raised after e rotation begins. The rotary-armature is provided with a so-called interruptornger 141 that separates the interruptorsprings' 112 and 143 whenever the rotaryarmatnre is attracted., and also with a rotary-armaturer 144 that exercises eertain contrilingY over the armature 145 o one o t e operating magnets, namely the private-magnet-146. The said private-armature 145 works in a'vibratory manner about a horizontal axis that pases through the supporting points 147. This armature is formed with a forwardly-projecting arm 148, the latter ha two Het surfaces in an approximately orizontal plane. Furthermore, the end -14:9 of the arm 14B 's bent downwardly at a right angle, and said arm 148 carri certain mechanical details, namely a lateral arm 150 which is designed to control circuits comprising the private-springs 151, 15'2 and 153, and a tooth-escapement which includes tivo exible springs 154 and 155 each of which is riveted b one end to the arm 148, one on the upper si e and the other on the lower. The upper spring is straight and has formed on its end two tooth projections 156 and 157 which extend downwardly, while the lower one is bent down and at a right 01e again to the front. This double angle ofiihe lower spring is so designed that the latter may clear the bent portion 149 of the privatearm, against which portion the said spring rests with a d of tension, and so that space is afford in ront of said bent portion to receive two other tooth-shaped upwardly-projecting pieces 158 and 159 that are formed on the forward end of the escapement-spring 155, and which are sustained in juxtaposition to the upperl teeth, but slightly to the rear thereof. A. retracting-spring 160, suitably located, holds said armature normally away from the privatemagnet pole-piece. A well-known auxiliary switc mechanism common to such switches is the so-called side-switch. It is shown in connection with the first-selector A and comprises an arm 161 which is secured to the switch-frame in such a manner that it may be made to swivel about a vertil axis that paes through the pivots 162. The right; extremity of said arm is drawn out into a finger 163 that works in conjunction with the escapement-teeth previously described. Said teeth, in a manner to be explained, convert the outward movement of the side-switch into a ste by-step motion, which movement is pr uced by a retractmg-spring 164.

dt the base of the inger 163 a lug 165, which is bent to the front, is adapted to strike the cam 81 at a suitable time. Whenever the shaft is rotated, however, said cam 110 is carried beyond the reach of the said l and after that the finger 163 simplyr falgls against the tooth 159. Near its left extremity the arm 161 carries a number of wipers 166, 167, 168 and 169 suitably mount- 115 ed upon a pin 170 and insulated therefrom and from each other. Said wipers are known as the side-switch-wipers, and are adapted to be operated by the private-magnetn and escapelnent device previously de- 120 scribed. If the private-maget is energized once, the private-armature is drawn down once and then restored to its normal position. The escapexnent-iinger 163 paes from behind the tooth 158 onto the rear of the 125 tooth 156, upon the downward stroke of the private-armature 145, and from behind the latter tooth upon the return stroke. As soon as the escapement-nger clears or disengages the latter tooth, the retractng-spring 164 130 draws the side-switch to the second position where it is stopped by the lug 165 when 1t strikes the cam 81. Immediately, then, as will be shown, the rotary-magnet becomes energized, the shaft is rotated, and the cam passes out of reach Yof the lug 165; and the finger 163 of necessity falls against the tooth 159. because of the tension in the spring 164. The rotation of the shaft results when the rotary-armature 135 is attracted by the rotary-magnet: at the same time, however, the rotary-armature-finger 144 depresses the private-armature 145 and causes the linger 163 to disengage from the tooth 159 and to advance against the tooth 157, and then, as

the rotary-armature returns to normal position. when the rotary-magnet denergizes, the vprivate-armature, upon followi 0 the linger 1-11, permits the escapementger 163 to escape from Athe last tooth 157, at which instant the side-switch passes to third position with the said finger resting against the side-switch-stop 171..Y In their normal positions, the side-switch-wipers 166, 167, 168 and 169 engage, respectively, with the contact-points 172, 173, 17-1 and 175. This position is known as the iii-st position of the side-switch, at which time it will be seen that the finger 163 is held behind the eseapement-tooth 158. In the second position, while the said finger is between the teeth 159 and 15S, the said side-switchwipers engage instead with the contactpoints 176, 177, 178 and 179, respectively; and when the said nger 163 falls against the stop 171, the wipers change their positions and more into contact wit-h the contactpoints 180, 181, 182 Vand 183, respectively. Between the pivots 162 and the wipers-supporting pin 170, a rearwardly-extending arm 184 on the side-switch-arm 161 supports on its end, pirotally, one end of a link 185; the other end of which latter,Y being bifurcated, engages with the `lower end of the double-dog-arm 129, which latten is constructed somewhat in the shape 'of an inverted T. Should the release-magnet be energized while the side-switch is in third position, and, of course, while the shaft is rotated, the release-link 119, being, attached to the release-amature 123, is thrust forward and catches the lug 130 in the aperture 120. Then when said release-armature is restored, the spring 124, as before described, withdraws the dog 128 from the longitudinal ratchet-teeth 81. At the same time, the arm 129 drives back the link 185, which latter then rotates the side-switch-arm 161 about the pivots 162, against the tension of the side-switch retracting-spring 164, and thus drives the finger 163 between the springs 154 and 155 and into a position behind the tooth 158,Y locking the side-switch in the first or normal position. The switch-shaft being un- 52- locked by the removal of the dog-support 128, and being thus left free, is rotated by the coil-spring 90 until the end of the shaftrest enters the slot- 86, at which time the shaft drops to its normal position. Therefore,.after the switch has been operated, the= energization and deinergization of the release-magnet is sulicient to restore the switch completely to its normal position. The Erst-selector is also provided with a vertical-private-normal-relaj. 186, and with a rotary-private-normal-relay 187. Each of these relays, by means of their corresponding armatures 188 and 189, has control of a set of two springs 190 and 191, and 19'2 and 193, respectively. These armatures, and the armatures 95, 96, 101 and 106 of the line and bridge-cut-o and back-release relays are similarly and suitably pivoted from points at their elbows; and when the magnet to which the armature is allotted is energized the end of said armature isoperated so that it travels away from the magnet. It is common practice, in u these first-selectors, toallot one to each line. With such arrang ment, the subscriber line-conductors usually terminate normally in side-switch-wipers similar to the side-switch-wipers 168 and 169, the vertical side of the line terminating in a wiper corresponding to the side-switch-wiper 168, and the rotaryside of the line terminating inv a wiper'corresponding to the sideswitch-wiper 169. In'this system, however,

,and although the vertical side of the line terminating in the first-selector A leads to the side-switch-wiper 168, the rotary side ends in the switch-shat-spring 92; but when the switch-shaft is raised and the springs 92 and 91 are brought into contact the rotaryline-conductor is extended to the usual sidemuchfwiper 16e.

The connector is of a well-known general type and adapted to perform the duties a1- lotted to it in this system. Manyvof the mechanical operations, as well as many of the circuits are very similar to those of the first-selector, and the general movements are nearly identical. The line and private banks will be at once recognized, as well as the vertically-disposed switch-shaft 200. Being identical with the first-selector switch-shaft, the latter is provided with the line-wipers 201 and 202, private-wiper 203, cam 204, longitudinal and circular ratchetteeth 205 and :296, respectively, the normalpost-armk 207, and the coiled Spring 208. The said circular ratchet-teeth, it will' be seen, are trarerseclby the usual longitudinal slot :209 into which the end of the shaft-rest 210 projects. The normal-post-arm 207 has under its control a spring 211, which, while the shaft is down, is kept. out of contact with the contact-point 212, but with which latter it engages when the shaft is in o eration. The vertical movement of sald shaft is, of course, produced through the 25 ward to catch the said lug medium of the vertical-magnet 213, which latter, as usual, is provided with a verticaL amature 214, having a vertical-arm 215, e and a. vertical-pawl 216, the said verticalarm being supplied with the L-sha-ped piece 217. The release-magnet 218, unlike the release magnet of the first-selector, has its armature 219 on the right side instead of on the left side, which armature is constructed 10 with an elongated front member 220 that reaches as far as the middle section of the double-dog 221. The release-link 222 is, as usual, under the control of the L-shaped piece 217, but is permanently secured to the switch-frame at the inner end 223. The

vertical and rotary locking-dogs 224 and 225, respectively, of the double-dog 221, will be recognized, as well as the side-switch releasing-arm 226 and, on the upper side of the bodyr of said double-dog, the lug 227 the. double-dog of the iirst-selector-so that the lug w is driven under the aperture 228, in which latter the lug is caught by the release-link 222 as stated. The double-dog 221 when thus locked is prevented from returning to its operative position when the release-magnet becomes denerglzed. The rotary-magnet 230 has a rotary-armature 231 that is quite simple. This latter is provided with a rotaryarm 232.11pon the ex- 49 tremity of which the rotary-pawl 233 is located. The rotation of the shaft each time that the rotarymagnet is energized is produced in a manner similar to that described in connection with the irsbselector. The

private-magnet 234, private-armature 235,

236 and 237, escapement-teeth 238, 239, 240 and 241 and the arm 242 are identi cal with similar parts of the first-selector. The saidarm 242, however, controls the 5 privatesprings 244, 245 and 24e, so um when the private-armature 235 is down the ilst two of said springs are separated and the last two brought into contact; and when the said armature is up the reverse takes pIace-thatisthesprings243and244close and the springs 245 and 246 separate. In the side-switch of the connector the sideswitch-arm 247, esca ent-linger 248, camlug 249, side-switch-stop 250, retracting- .o sp1-ing 251 on one side of the pivots 252,

member 253, link 254, side-switch-wipers 255, 256, 257 and 258, together with their corresponding contact-points 259, 260 and 261;.262, 263 and 264; 265, 266 and 267;

$5 and 26S, 269 and 270 on the other side, conform to like parts of the first-selector sideswitch. Among the relays of the connector the vertical-line-relay 271, by its armature 272, can flex the spring 273 against the grounded spring 274 and the sprin 275 toward the spring `276, when said re ay is energized. The rotary-line-relay 277, in the same manner, by its armature 278, when said relay is magnetized, forces the spring 279 against the same ground-spring 274 and permits the spring 276 in turn to bend toward the spring 275. Saidtwo springs 275 and 276 are so adjusted that they come into contact only when the two armatures 272 and 278 are attracted simultaneously.

The ringer-relay 280 .is a feature common to all connectors of the type under consideration and is adapted when energized to disconnect the terminals of the called line from those of the calling line and to place across the former the terminals of the ringer-generator J. This operation is accomplished through the medium of the armature 281 which has control of the ringerrelay-springs 282, 283, 284, 285, 286, 287, 288 and 289, some of which are the terminals to which reference is made above. In addition, the connector is provided with a dierential-relay 290 having tvo windings 291 and 292. One end of the said winding 292 is connected through the \e.rticalline relay 271 with the `vertical. side of the main talking line, and the other end of said winding is connected with the non-grounded terminal of battery B. The second winding 291 is connected at one end through the rotary-line-relay 277 with the rotary side of the main talking line, While the other end is connected with the ringer-relay-spring 288 of the ringer-relay 280. Said spring 288 is normally in contact with a second spring 2,89 that is connected with a third spring 293 which is under the control of the amature 294 o'f the socalled polechanging.-relay 295. Furthermore, said spring 293 is located between two other springs 296 and 29T and is normally in contact with the latte;- Which constitutes the non-grounded terminal of battery B, but the said middle spring 293 may be shifted by the armature 294 away from the spring 297 and into contact with the spring 296 which. when the. connector-sideswitch is in third position, is directly connected with ground. By means of such construction the differential-relay-coil 292 may be energized only1 when the vertical side of the main line is connectedto ground; but the other coil 291 may be energized when the rotary side of the line is grounded or when the spring 293 is grounded against the spring 296-that is. while the side-switch-wiper 256 is in third position. -In one case the current will How in one direction, and in the other case in the opposite direction, in this last coil, so that A the two windings 291 and 292 may be ener` gized to neutralize or reinforce each other, depending upon the direction in which the current is made to flow. Also, with the arrangement described, the two ends of the coil 291 may be grounded at the line and at the spring 293 simultaneously, rendering said coil or winding, together with the rotury-line-relay 27T, short-circuited or shunted through ground for purposes to be disclosed hereinafter. Said diifereutial-relay can, when energized. and by its armature 29S, separate the springs 299 and 300 und close the springs 301 and 302. The former normali; rest in contact and the latter out o contact. In addition, the connector is given a retardation-coil 303 which is used to balance the line and to regulate the iow of current in circuits in which said coil may be included. There are also two condensers 304 and 305 which are included in the main talking circuit, one on the one side of the line and the other on the other.

ln Fig. 1 the called rst-selector A* being identical with the calling first-selector A, the former will be recognized without further description. For the sake of simplicity, however, the private-normal-relays (similar to the private-normal-relays 166 and 1ST of the first-selector A) have been omitted, but the springs 30T, 30S and 309 which they control are shown. Hereinafter it will be disclosed how the bridge-cut-ol-relay 310 is maintained energized while a connector is connected with the called line. The purpose for so keeping said relay energized is temporarily to destroy or open a bridge that normally exists between the side-switch-contact-points 311 and 312 and that includes the line-relays 313 and 314 in series with the bridge-cutorelaysprings 315 and 316, by separating the spring 31? from the said springs 315 and 316, which spring 31T is connected to the non-grounded terminal or batter)` B. The object in this construction is well known.

To a full understanding of the construction and operation of the various parts of my invention, und the circuits involved when one subscriber calls another subscriber, :1 description will now be given of the process bj: which the subscriber #320 calls or connects with and rings or signais the subscriber at station #130. In order to make a call the subscriber at the sub-station first removes his receiver 2 from the switch-hook 3; then the cam-arm 5 disenguges from the ringer'circnit-spring 24, and the normally-closed circuit through the ringer 9 at the sub-station #320 is opened. Furthermore, as soon as said cam leaves the spring 24 the springs 26, 27, and the springs 2S, 29 come into Contact. At the same time the spring 32 leaves the spring 33 and is driven into electrical connection with the springs 3l and 30 by the cam-arm 7. Furthermore, the so-called ground-springs 34 :1nd 35 are permitted to engage as soon as the cam-arm 6 passes away from the groundspring 35. At once n ground connection is completed between the ground-post 46 and the ground-terminal GJ. The said connection may be traced from the said ground G through the sub-station relay-springs 21 and Q0 to the conductor 31S, thence to the groimd-springs 35 and 34 and over the conductors 319 and 320 to the said ground-post. The subscriber then proceeds to establish his connection by pressing the vertical-button once, and then the rotary-button 41 once, by which operations the first-selector extends the subscribers line through some idle trunk to the connector C. .it the next movement the operator presses the vertical-button 40 again three times, and the rotary-button 4l once. By this the connector-switch shaft is raised to the level (the third level) in which is found the terminal of the desired subscriberis line, and then at the grounding of the rotary line the side-switch passes to second position. The calling subscri ber proceeds by pressing for the lan time the vertical-button 40 ten times, and the rotary-button 41 once, thereby causing the connector-wipers to be rotated into connection with the desired line, causing the eX- tended line-conductors to be connected with said wipers, and thus conznpletiner the desired connection. When the vertilfliutton 4:0 is pressed once for the {i1-st time the vertical line-conductor 321 is thereby grounded once and the vertical-line-relay 93 of the rstselector A is energized once. The current in this energizing circuit passes from ground Gr through a circuit already described, to the ground-post 46, thence to the spring 42, verticalline-conductor 3'21, vertical-sideswitch-wiper 168, contact-point 174, conductor 32:?, vertical-line-relay 93, conductor 323, bridge-cut-oE-relay-springs 103 and 10i to the battery-lead 324, and through battery B to ground G. Upon being energized, the vertical-line-relay attracts its armature 95, and forces the linerelay-springs 99 and 97 into contact, by which operation the verticalmngnet- 109 is in turn energized. The current in this last energizing circuit passes from ground G: through the said springs 99 and 9T, conductor 325, private-springs 152 and 151, conductor 326 and vertical-magnet 109 to the battery-lead Z324. thence through battery B to ground G. Upon being magnetized the vertical-magnet attracts the vertical-armature 110 once and raises the switch-shaft one step. At this step, of course, the release-link 119 is withdrawn from the double-dog 12-5 by the L-shaped piece 118, at which time the dog 12T engages one of the circular teeth 85 and prevents the shaft from falling to its original position- At the time that the normalpostarm leaves the spring 91, the latter passes into engagement. with the contact-point 92, and the rotaryline-conductor 32T which is normally open at the said coutact-point 92 is then extended to the rotary-side-switch-wiper 169. After the shaft has been raised one step in this manner the switch-wipers will he found opposite the first contact of the first level of their respective banks 'T5 and 76, but out of engagement ith the bank-contacts. The rotary-button l is then pressed once, and the rotaryiinerelay 94 becomes energized once. The current in this case passes again from ground G1 to the ground-post 46 and thence to the spring 43, rotarvline-con ductor 32T, springs 92 and 91, conductor 32S, side-switch-wiper 169, contact-point 175, conductor rotary-line-relayY 94, conuctor 330, bridge-cut-oirelay-rings 102, 103 and 10-1 to the batterylea 324, and through batteryY B to ground G. The rotary-line-relay being enervized, the linerelay-springs 98 and 99 are Forced into contact, and as a result the private-magnet 146 is magnetized. The electric current here tion-s from ground G2 through the springs 99 and 9S, conductors 331 and 332, and prirate-magnet 146 to the battery-lead 324.l thence through battery B to ground G. The privatem-mature 145 being attracted once and restored, the escapement-tooth 158 rs't clears or disengages the escapement-nger 163, which latter then falls against the second tooth 156, and when the armature returns to its normal position the latter tooth in turn clears or disengages the escapementlinger 163. At that instant the side-switch is drawn into second position by the retract4 ing-spring 164, with the cam-lug 165 resting against the cam 81.

lt will understood that the prongs of the biiucated end of the link 185, which rest. upon the T-shaped extremity of the side-switch releasing-arm 129, are of Sullicient length to permit the said releasingarm 129 to more from the position that 1t holds when the `double-dog is held normally lod-:ed by the release-link 119 to the position it aumes when the doubledog is released. without disengaging from said prongs. The moment that the side-switch passes from {i1-st to second position a circuit is completed through the rotary-magnet 1I-E2 (as will be shown) when the sideswitchwiper 166 closes with the contactpoint 1TB. The current then flows from the ground terminal Gf* to the contact-pointI H5. through the side-switch-wiper 166. conductor 333, rotaryniagnetil 134, interruptor-springs 11.2 and 143 through the second rotarymagnet-coil 1313 to the bat-'terylead 32% and through the battery B to ground G- The rotary-magnet 132 then attracts the rotary-armature 135 and forces the rotary-paw] into engagement with one of the longitudinal teeth 84, causing the shaft to rotate one step. Just at about the time that the rotary-armature strikes the rotary-magnet pole-pieces the rotary-dov 128 falls behind the first of the lonq'itudina teeth, in a manner already descri to prevent the shaftfrom returning to its normal position when the rotary-magnet becomes denergized. and at. the same instant the interrupter-Iinger 111 forces the interruptersprings 142 and 143 apart, destroying or opening the energizing circuit through said magnet. When the rotary-pawl 139 advances to engage the longitudinal teeth, as described, the rotary-armature-finger 144 comes into contact with the private-armature 145, depressing the latter at the same time that the rotary-pawl produces a rotation of the shaft. As the shaft. rotates, the cam S1 very soon passes out of reach of the cam-lug 165, permitting the escapement- .finger 163 to fall against the tooth 159 before the rotary-armature4inger 144 depresses the private-armature 145 too far. Very soon, however, the said tooth is carried below the finger 163, which latter then falls against the upper tooth 157 at about the time that the shaftwipers are rotated onto the rst contact of the first level of their respective banks. As soon as the energizing circuit through the rotary-magnet is interrupted the rotary-armature to return to its normal tion, and prirate-armature also f back, following up the ceding movement of the rotary-armature-finger. The tooth 157 also clears or rages the escapementnger 163, and the side-switch moves into third position with the escapementtn r 163 against the side-switch-stop 171. he shifting of the nde-switch takes place just before the interrnpter-inger permits the interruptersprings 142 and 143 to rengage, so that the energizing circuit that has been described through the rotary-magnet is destroyed at a point between the sde-switchwiper 166 and the contact-point 176. When the action of the rotary-armature ceases permanently the calling operation of the rsbselector comes to an end, the line-wipers 'TS and T9 haring seized upon an idle trunklne similar to the trunk-line that terminates at the tenth terminal of the first level of the linebank 75, the conductors 334 and 335 of which line lead to an idle connector. The seized trunk is protected from further seizure by a guarding potential established at the private-wiper S0, and, therefore, at the lirst contact of the private-bank T6, and at all other private-bank-contacts connected in multiple with said irst Contact. Said guarding potential is established by reason of u connection between the ground terminal of battery B and said contacts, by Way of P Ae5 tentlal at the first contact which the private- Vthe grounded terminal G, side-switchwiper 16T, conductor 336, back-release-relay 105, conductor 33 and private-wiper 80. Furthermore, by the same Ground connection G. and through the si e-switch-wiper 167. conductor 338, private-normal-relaysprings 193 and 192, and private-normalconductor 339, a guarding potential is established at the connector-private-banl; corresponding to the calling line, that no calling subscriber may interfere with the callin line for the time being. Similarly, shoul any first-selector appropriate to its use a second trunk-line of the same level of the line-bank 75. a guarding potential will then appear at the second private-contact of the firstlevel of the private-bank 76. as Well` as at all other private-contacts in multiple. And should a third first-selector seize the third trunk on the same level a guarding potentiel will appear also at the third private-contact of the first level; and if the fourth, fifth, etc., through the nine trunks be occupied, guarding potentials will be found at the fourth, fifth, etc., and through the ninth private-contact-terminals of the liz-st level of the private-bank. Therefore, if the first nine trunk-lines of the first level are busy a guarding potential is found at each one of the first nine private-contacts of the first level of the private-bank T6. If this condition exists at the time that the calling subscriber .#320 grounds the rotaryline-conductor by pressing the button 41- some other subscriber, of course, holding the first iz'unk of the first level-the rotation of the shaft will not terminate as soon as the Wipers move onto the first terminal of the rst level. The first nine privatecontacts grounded, then when the calling subscriber grounds the rotary side of the line, as described, the side-switch trips into second position as before; but the rotation of the shaft does not cease until the wipers have been carried beyond the last of the busy trunk-lines, in this case onto the tenth terminal of the Erst level of the banks in question. This continued or selective rotation takes place in the follo 0' manner: The energizing circuit through i e rotarymagnet being closed as pointed out, at the juncture when the side-switch-wiper 166 engages with the contact-point 176, the rotaryarmature is attracted by the rotary-magnet 132, and the shaft is rotated one step, in the manner described, so that the line and private wipers are rried into engagement with the first terminal of the first level of their respective banks. At the same time the private-armature is depreed by the rotary-armature-Enger 144, and the interrupter-springs 142 and 143 are, at the end of the stroke. e paz-ated by the interruptorlinger 141. There a .qu owiper meets.| a circuit is thereby completed through the private-magnet 146, which extends from the ground terminal G of the battery B, through the private-wiper of whatever first-selector is occupying the first trunk of the rst level in question, through the bank-multipling conductors to the contact-point with which the private-wiper 80 is in engagement, through conductor 337, winding of the back-release-relay 105, oonductor 336, side-switch-wiper 167, contactpoint 17T, conductors 340 and 332, privatemagnet 1&6. and through battery B to ground G. The private-armature is thereby reta ined in a depressed condition, even after the energizing circuit of the rotary magnet is broken at the interrupter-springs, and while the rotary-armature-nger returns to its normal position in response to the retracting tension of the rotary-armature reract-ing-spring 137, since the escapementfinger 163 is held by the upper foremost escapement-tooth 157. The side-switchwiper 166 being. therefore, retained in engagement with the grounded contact-point 176, it follows that as soon as the interrupter-springs come together the energizing circuit through the rotary-magnet. is completed once more. As a result, the rotaryarmature is again attracted, the shaft is rotated one more step, and the private-wiper is moved onto the second terminal of the first level of the rivate-banlr 76. Said second contact also ing grounded, it follows that the energizing circuit through the private-magnet is maintained, so that the sidesvfitch is not liberated when the rotaryarmature again returns to its normal position. Clearly, then, the shaft will be rotated in a step-by-step manner as long as the private-wiper continues to meet with grounded private-contacts After being rotated onto the ninth contact the privatexviper is rotated one more step into engagement with the tenth Contact of the first level of the private-bank; but this last contact being devoid of guarding potential, it is evident that as soon as said wiper leaves the ninth contact and passes onto said contact tlns magnetizing circuit through the private-magnet is broken. occurs at )ust about the time when the rotary-amature is at the end of its attractive stroke; so that the private-armature that has up to this time held the side-switch in its second position (by the magnetizing force which has now disappeared from the private-magnet) falls back upon the rotary-armatnre-lnger 14% and follows said linger as the rotaryarmature returns to its normal position. Between the time that the private-armature 1s released bythe private-magnet and the time that the rotary-armature fully regains its normal position the escapement-nger 163 which, during the rotation of the shaft,

has been resting against the foremost tooth of the upper escapementspring, dlsengages from said tooth, permitting the side-switch to pass into third position. It is then that the side-switch-wipers leave the contactpoints 176, 17T, 1'4'8 and 179 and pass onto the contact-points 180, 181, 182 and 133. The shifting of the side-switch the disengagement of the sideswitch-v1per 166 from the contact-point 17 6 occur )ust before the interrupter-sp s 142 and 143 re-engage, and therefore t e circuit through the rotary-magnet is permanently broken 1n order that no further rotation of the shaft may take place during its operation. At the same time the engagement of the wlper 16T with contact-point 181 provides the prlvate-wiper 80 with guarding to protect the trunk seized by the hne-wlpers 5S and 79. Of course, it will 'be clear that when the wipers 168 and 169 arrive on the sideswitch contact-points 182 and 183 the line-conductors 321 and 32T are extended to the connector C over the conductors 334 and 335.

It may be stated at this point that if after the subscriber has begun to call, and before the first-selector has trunked to the connector, he should desire to discontinue hls call he may interrupt the operation of the selector and restore it by simply hanging his receiver on the switch-hook. This may occur while the side-switch is in the first or second position, it matters not` As a result of restoring the receiver both sides of the main line are ounded for a moment. If this occurs while the side-switch is in first position the vertical and rotary line-lays 93 and94are tized at the same time over circuits that are already known, and as a result the release-ma et 122 of the first selector is energized an denergized and the ector is restored. It has been described that in its action the releaseamarm 4, as it passes down when the receiver is restored, llexes the release-springs 38, 37 and 36 ing? correxltact for a moment. dOf these rm'gsfe ease-rings' 38:11137,re gectvely, are connzted with the vertical and. line-conductors 321 and 327, while the third release-spring 36 is connected to ground G1. Therefore, as a result, the temporaryA engagement of these three springs sends a ground impulse over each side of the main line with the usual effect upon the iirst-selector line-relays 93 and 94. The current througl the verticaldinerelay, during its energization, passes from ground G1, through the springs 21 and 20, conductor 318, springs 35 and 34, conductor 319, release-springs 36, 37 and 38, contacbpoint 45, and spring 42 to the verticalline-conductor 321, thence through the verticallinerelay 93 to battery B and to ground G. Through the -rotary-line-relay 94, the current also Hows from ground Gr1 to the release-spring 36. passing thence to thespring 37, contactpoint spring 43, and to the rotary-line conductor 327, switch-shaft-springs 92 and 91, side-switch-wiper 169, conductor 329, thence through the rotarylne-relay 94 to the non-grounded terminal of the battery B and to ground G. The rotary-line-relay being energized the private-magnet is energized also and, while thus energized, maintains the private-springs 152 and 153 in contact. The vertical-line-relay being energized, and the linesrelay springs 9i' and 99 being forced together at a time when the private-springs 153 and 152 are in contact, a combination of circuits provides a magnetizing circuit for the release-magnet 122 as follows: from ground through the line-relay-springs 99 and 97, conductor 325, private-springs 152 and 153, conductors 341 and 342, release magnet 122 to the batterylead 324, and through battery B to ground G. As a result, the release-magnet attracts its armature 121, and the releasedink catches the double-dog-lug 130; then as the releasecam-ar1n 4 on the vswitch-hook 3 clears the l 39 on the release-spring 38, the three re ease-sprin 36, 37 and 38 necessarily fall apart, at which instant the ground connections to the main line-conductors are destroyed and the line-relays 93 and 94 of the first-selector are denergized. Upon this deenergzation there follows also the denergization'of the private-magnet 146 and of the release-magnet 122. As already pointed out, when the release-magnet becomes energized and denervized the rst-selector is released by the release-armature retract-ingspring, which latter restores the double-dog 125, and retracts the dogs 127 and 12S, at which instant4 the switch-shaft is restored. It will be understood that if the release oc curs, however, while the rotation of the switch-shaft is taking place the vertical and rotary line-conductors will be grounded as before; but the sideswitch-wipers 16S and 169 being in second position and in contact vgith the contact-points 178 and 179, respectively, the vertical-lne-conductqr is then open and the grounding of said conductor at this time. produces no effect. But the r0- tary-hneconductor, however, being connected the vertical-line-relay 93 by way of the springs 92 and 91, contact-point 179, conductor 343, contact-point 174 and conductor 322, it follows that the grounding of the 'rotary-lineconductor magnetizes said verticalrelay. New, since the privatemagnet, while the private-Wiper is passing over grounded contacts, is retained magnetized. the private-springs 152 and 153 are main; tamed in contact. Therefore, the groundlng of the rotaryline-conductor while the side-switch is in second position produces a magnetization of the vertical-line-relay,

fore, the releasing of the while the said private-springs are together, and, as a result already pointed out, the magnetization of the release-magnet 122 follows. But as soon as the release-springs 36, 37 and 3S at substation disengage the ground-circuits to the line are destroyed, the release-magnet is denergized and the switch is released the same as usual. The shaft, now deprived of the lock furnished by the rotary-locking-dog 128, is rotated back toward normal rotary position upon the end of the shaft-rest- 87, and at the instant that the normalpost-arm S8 strikes the normalpost S9 the said shaft-rest enters the longitudinal slot 86, at which time the shaft, losing its only support, falls to normal position, leaving the switch completely restored. Of course, it will be plain that the magnetizing current through the release-magnet in this last. case passes, as before, from #round Gr2 through the springs 99 and 97 and to the private-spring 152, thence through the priv vate-spring 153 to the release-magnet 122 and through battery B to Ground G. Thererst-selector while ille sideswitch is in Erst position results from energizing both the vertical and rotary line-relays simultaneously.

The release during rotation of the shaft and, therefore, while the side-switch isin second position results from the grounding of the rotary lineconductor and the energizing thereby of the vertical-linerelay while the privatesprings 152 and 153 are in contact; but after the first-selector has selected the trunk and the side-switch is in third position. since none of the line-relays remain in connection with either of the sideswitchmripers 16S or 169, and as there is no connection between the adjoinin' contactpoints iss, 17s and 174, and 183,1?9 and 175 over which said side-suitch-wipers slide, the release is then produced in another manner by means of the so-called back-relearelay 105 over-'what is known as a trunk-release conductor, as will be pointed out. After the calling line-conductors are extended m the connector the operation of the calling device for the cond digit causes the verticallineconductor 321 to be grounded three times when the vertica1-button -10 is preed three times. In this Way the vertical-lne-relay 271 of the connector is energized three times A current then flows from ground Gr1 at the callingsub-station to the ground-post 46, through the spring 42, verticaldineconductor 321, side-switchwiper 168, contact-point 182, conductor 3M, verticalprivate-normal-relay 186, conductor 345, vertical-line Wiper 78, vertical trunkconductor 334, vertical-ljne-relay 271, conductor 346, 292 of the differentialrelay 290 to the battery-lead 324 and through battery B to g'round- G. The verticalline- 35 relaythen attracts its armature, and the latter presses the line-relay-springs 273 and 274 into contact, thereby establishing a circuit through the vertical-magnet 213. Through the said vertical-magnet the energizing current passes from ground Grs through the line-relaysprings 274 and 27 3, conductor 349, private-springs 244 and 243, conductor 350, side-switch-Wiper 255, contact-point 259, conductor 351, and verticalmagnet 213 to the battery-lead 324 and through battery B to ground G. The verticalmagnet on attracting its armature three times raises the shaft 200 three steps and brings the wipers 201, 202 and 203 opposite the first contacts of the third levels of their respective banks. The subscriber again presses the rotarybutton 40 once aud grounds the rotary-line-conductor 327 once. at which time the rotary-linerelay 277 of the connector is energized. The current in this last circuit paes from ground G to the ground-post 46, through the spring 43 and rotary-line-conductor 327, first-selector sWitch-shat-springs 92 and 91, conductor 328, side-switch-wiper 162. contact-point 183, conductorv 352, rotary-private-normalrelay 187, conductor 353, rotary-wiper 79, rotary trunk conductor 335, rotary line relay 277, conductor winding 291 of the dil'erential-rela)T 290, conductor 355, ringerrelay-springs 288 and 289, conductor 356, pole-changing relaysprings 293 and 297, thence through battery B to ground G. As the linerelay 277 is energized the line-relaysprings 279 and 274 are brought together and the private-magnet 234 is energized by current flowing from the ground Gs through the said springs 274 and 279, conductor 357, private-magnet 234, conductor 35S, polev changing relay-springs 293 and 297 'to the battery-lead 324: and through battery B to ground G. When the amature 235 of the private magnet 234 falls back, it permits the connector-s1deswfitcb to pass to second position, the side-switchwiper 255 passing from the contact-point 259 onto the contact-point 260, and the sideswitchwiper 256 from the contact-point 262 onto the contact point 263. The shifting of the sidesswitch-wiper 255 produces a. change in the circuits of the com nector whereby` when the vertical-button 40 again is pressed ten times for the last digit, the rotarymagnet 230 instead of the verticalmagnet is operated when the line-relay springs 27 3 and 274 are brought into contact. Each time the said springs close a current is sent from ground G"s through the said springs 274 and 273 and the privatesprings 24:4 and 243 to the side-switch-wiper through the contact-point 260, conductor 359, rotary-magnet 230 to the battery-lead 324, and through battery B to ground G. At each pulsation the rotary-magnet attracts its armature 231, rotating the shaft 200 one step at a time and sliding the wipers 201,

202 and 203 along the third level of the banks which the),y engage. Then for the last time the rotary-button 41 is pressed once. As a result, the rotary-line-conductor 327 is again grounded, and again the rotary-linerelay 27T of the connector is energized once. The said relay in turn causes the privatemagnet 234 to become energized and to thus permitthe side-switch to pass to third position with the wipers 255, 256, 257 and 25S, respectively. in contact with contact-points 261,26is267 and 270. The closure of connection between the side-switchwipers 25T and 25S and contact-points 267 and 270, respectively. connects the calling snbscribers ex tended liue-conductors 334 and 335, through the condenser-s 304- and 305, with the vertical and rotary line-wipers 201 and 202. respectively. and, therefore, with the normal-conductors 361 and 36:2- that constitute the terminais of the called line.

The engagement of the side-switch-wlper 256 with the contact-point. 264 places a guarding potential at the private-viper 203 at the tenth private-contact of the third level of the private-bank 360, and at all other private-contacts in multiple, to preclude any other connector from cu v m upon the. called line #130. The estab shment o this guarding potential over the called line not only protects it from further seizure but also forces a current through the bridge-cutoirelay 310 of the first-selector of the called line, that the latter, through its amature, may separate the bridge-cut-ol relay-springs 315, 316 and 31T, for reasons already stated The energizing circuit through the said bridge-cut-ot-relay extends from ground Gs to the contact-point '264, thro the sideeswitch-vviper 256, conductors 363 and 364, private-wiper 203, prirate-normal conductor 365, rotary-priyatenormal-relay-springs and 309, conductor 366, side-sivitch-wiper 36', conductor 368, bridge-cut-otf-relay 310, through battery B and to ground G. It will be noticed that each time that the vertical or rotary linerelay has been energized the energization has occurred in series with one of the windings of the dilerential-relay 290. The energizing of said dierential-relay hitherto has played no part in the operation. It will be shown. however, at a proper time that the energization of the differential-relay is essential to certain hereinafter described operations. Not only has it been shown that the vertical-line-relay is energized in series one of the windings of the differentialrelay, but also in series with the verticalpriratc-normal-relay 186 of the first-selector: and the rotary-line-relay also in series with the Yrotary-private-norinal-relay 18T of the same selector; but neither of these relays up to the prent time has played any part of signilicance. Their utility will be set forth in the following description. Connection between the ca 'ng and called lines having been established the calling subscriber is in a position to si al the called line by pressing his signaling-button 15.

But before oing further it may be explained that 1f for any reason the called line is busy at the time that the callino' subscriber grounds the rotarydine-conlductor 327 for the last time, as explained in the matter immediately preceding, to transfer the connector-side-switch from second to third position and to complete the connec tion, the connector is released. For instance, if the line #130 has been called by any connector there will be a guarding potential at the tenth private-contact of the third level o the privatebank 360 corresponding to the line of the substation 130. Or, on the other hand, if the firs# ector A1 of the called line is being used, the same private-bank-contact will be connected to ground from the instant that the side-switch paes to third position and the side-switchwiper 36T finds the grounded contact-point 369. Said arding potential will reach the private-ba of the connector by way of the private-normalconductor 365. At any rate, if the private-wiper 203 nds a guarding potential at the tenth contact of the third evel of the rivate-bank 360 at the instant that the calEng subscriber grounds his rotaryline-conductor 327 for the last time, then instead of the side-switch being tripped into third position the connector will be released, because the private-magnet 234 on becoming energized as a iinal result of grounding the rotary-line-conductor 327 completes an energizxng circuit through the release-magnet of the connector when the armature of the said private-magnet forces the springs 245 and 246 into contact. The ener g circuit for the release-magnet extendgsrlom the grounded terminal of the battery B to the tenth contact of the third level of the connector-private-bank 360, through the rivate-wiper 203 to the conductor 364, sidesivitch-wiper 256, contact-point 263, conductor 370, private-sprin s 245 and 246, conductors 371 and 372, reease-magnet 21S. conductors 373 and 374, through the diferential-relay-springs 301 and 3&2-, to the battery-lead 324, thence through battery B to ground G. Since this occurs while current 1s iowing through the diii'erential-relaywinding 291, in series with the rotary-line relay 277, the dierentiahrelay 290 is there by energized; therefore, the springs 301 and 302, through which the releasing circuit extends, are maintained in contact. The connector-release-magnet being energized, the release-armature then moves the double-dog so that the lug 227 is caught and held in the aperture 228 on the end of the release-link 222. Of course, when the double-dog 221 is thus rotated the locking-dog 225 is withdrawn from the longitudinal teeth 205. The shaft is then free to rotate back to its normal rotary position because of the tension in the coiled spring 208, which rotation ceases only when the normal-post-arm 207 strikes the nonnal-post 375. At that instantthe shaft-support 210 enters the slot 209 and the said shaft of necessity falls to its normal position.

The release-armature, when it rotates the double-dog 221` at the same time swings the side-switch to its first position, about the pivots 252 of the latter, by means of the link 254 and the release-arm 226. The latter, by pressing the former back, forces the escapement-inger 24S back between the escapement-springs 236 and 237, where it is then caught behind the rearmost lower tooth 240 where it remains until the connector comes into use again. The restoration of the connector-shaft begins even while the release-magnet is in an energized state; but since the energizing circuit through said magnet comprises the private-wiper 203 and the side-switchm-'ipcr 256, it is evident that when the shaft rotates back toward normal position, and when the side-switchwiper 256 is forced away from the contact-point 264, the energizing circuit will then be destroyed at two points, at which time the connector-release-armature 219 regains its normal position. The calling subscriber, thinking he has established connection, presses the button 15 to ring or signal the called subscriber, with the result that the vertical-line-conductor is grounded. This produces, of course, an energization of the connector-rertical-line-relay 271 in the usual manner; and since the connector-side-switch is in Erst. position the latter relay produces in turn the energization of the connectorvertical-magnet 218, through a circuit that is already familiar when the line-relaysprings 273 and 274 are pressed into contact. When the S'gnaling-button is pressed the ground connection to the vertical-lineamductoi 321 is nog: estlblishd lhrpu h the nnpost46, utt ong te oowing cg'rirzuit: from ground Gr1 through the substation relay-springs 21 and 20, conductor 318, signaling-hutton-springs 18 and 16, primary circuit-springs 26 and 27, contactf point 45 and spring 42 to the vertical-line' conductor. As a rult, and by means previously described, the shaft of the connector is raised and the springs 211 and 212, which it controls by the norma1-postarm 207, are brought into Contact. Upon the engagement of these two springs 211 and 212 a circuit is completed through which a busy-signal current is transmitted to the receiver of the calling subscriber, which current may oriinate m any suitable apparatus comme y s used in telephone exchanges and comprising a coil 376 in which the said busy-signal current is induced. The path of the current may be traced from the coil 376 to the conductor 377, springs 212 and 211, conductor 378, contact-point 268, Y side-switch-wiper 258, ringer-relay-springs 283 'and,282, conductor 379, condenser V4305, trunk-conductor 335, rotary-line-wiper 79, conductor 353, rotary private normal relay 187, conductor 352, contact-point 183, side-switch-wiper 169, first-selector switch-shaft-springs 91 and 92, rotary-line-conductor 327, spring 43, contact-point 44, conductor 380, sub-station relay-springs 23 and 22, conductor 381, springs 31 and 30, transmitter 8, primary coil 11, signaling-button-sp 17 and 16, primary circuit-springs 26 an 27, contact point 45, spr-ini 42, verIcal-linemnductor 321, side-swit -wiper 168, contact-point 182, conductor 344, verticalprvatenormal relay 186, conductor 345, vertical-line-wiper 78, vertical-trunk-conductor 334, verticalline-relay 271, conductor 346, winding 292 of the differential-relay 290, battery-lead 324 and back to the coil 376. The calling sub scriber, learning that the desired line is busy, will then restore hisreceiver to its switch-hook, thereby grounding in a familiar manner, the vertical and rotary line-conductors 321 and 327. Grounding the former at the sub-station energizes, as usual, the verticallinerelay 271 of the connector and the dierential-relay 290. Grounding the latter at the sub-station energizes the ro. tary-line-relay 277 of the connector and reinforces or augments, in this case. the already energized dferential-rclay 290. The two line-relays 271 and 277 being energized simultaneously, and the dierentialrelay 290 bein energized as well, so that the differentialy-springs 301 and 302 are forced into contact while the trunk-releasesprings 275 and 276 are maintained connected, the release-magnet 218 is magnetized in series with the back-release-relay 105 of the lrst-selector A. This ene circuit extends from the ground terminal fiat the first-selector side-sw1`tchcontact-point 181, sideswitchwiper 167, conductor 336, backrelease-relay 105, conductor 337, private- Wiper 80, private-bank-conductor 382, trunkrelease-springs 275 and 276, conductors 383 and 372, release-magnet 218, conductors 373 and 374, and through the differential-relaysprings 301 and 302 to the battery-lead 324, and through battery B to ground G.

Of course, simultaneously with the energizing of the connector-releasemagnet, the rst-selector back-release-relay 105 is also magnetized, and the latter by attract its amature 106 causes the backrelease-re aysprings 107 and 108 to engage in contact. An energizing circuit is thereby established through the frsbselector release-magnet 122, in which the current paes from ground G through the back-release-relay-springs 107 and 108, to the conductors 384 and 342, thence. through the release-magnet 122 to the battery-lead 324, and through battery B and to ground G. The release-magnet of the connector being the release-arma.- ture 219 is attracted" and, as before, the double-dog is rotated or swung to its normal position away from the connector-shaft which then falls to its normal position, ,separating at the same time the busy circuit shaft-springs 211 and The firstselector release-magnet being energized the lirst-selector release-amature 121 is attracted, and the release-springs at the sub-station springV apart as the switch-hook reachesits lowest position. All the release energizlng circuits are then destroyed and the first-selector is fully restored in a manner that is already well known; and at the same time the connector-line-relays, as Well as the connector-release-armature, regain their normal positions, leaving the latter switch 1n readiness forV further use. But it has been described that the called line is notI busy and that the connection Ywith said line is completed. Therefore, when the signaling-button 15 is pressed, in a manner already stated, the subscriber grounds the vertical-line-conductor 321, as above, and the vertical-linerelay, through circuits already is energized. Since the side-switch of the connector is in third position, and the connector-side-switch-wiper 255 is in engagement with the contact-point 261, the engagement of the line-relay-springs 273 and 274, at the energizaltion of the vertical linerelay, produces in turn an energization of the ringer-relay 280. The energizing current passes from ground G5 through the said line-relay-springs 274 and 273, private-springs 244 and 243, conductor 350, side-switch-wiper 255, contact-point 261, ringer-relay 280, conductors 385 and 374, springs 301 and 302, to the battery-lead 324 and through battery B to ground G. The ringer-relay-armature 281 then forces delay-springs 283 and 286 away from the springs. 2Q and 285 and onto the springs 284 and 28T, at the same time separating the springs 288 and 289. A signaling or ringing current then passes onto the called subscribes line as follows: from the ringer-generator J to the brush 386, and thence over the conductor 387, through the ringerrelay-springs 284 and 283, sideswitchwiper 258, contact-point 270, conductor 388, rotary-line-wiper 2%, rotary-normal-conductor 362 of the connector-line-baxlk 389, rota,` ry-ljne-conductor 390spr'mg 3 contac-point`392, conductor 393, ringer 394, condenser 395, ringer-circuit-spring 396, switch-hook 39", conductor 398, contactpoint 399 and spring 400, vertical-line-conductor 401, vertical-normal-conductor 361,

vertical-line-wiper 201, conductor 402, contact-point 267, side-switch-wiper 257, ringerrelay-springs 286 and 28T and conductor 403, back to the brush 404 and to the generator J. The particular generator J, allotted to the connector C, produces a current of such frequency that only the bells 394 at the said sub-station will res ond. If the sub-station had been cal ed, a different connector would have been reached by the action of the first-selector A, which connector would have been one of a group provided with a ringergenerator giving current of a particular frequency capable only of ringing stations provided with ringers that respond to currents produced by said generator. Of course, any suitable signaling system may be employed. Although the current sent over the line to the sub-station #130 passes also through the ringing apparatus of the sub-station #230, no signal is given at the latter station. since the bells are'so adjusted that they do not respond to the current of the character used to signal the sub-station #130. As soon as the calling subscriber ceases to press the signaling-button 15 the ringer-relay becomes dee'nergized and the springs 283 and 286, respectively, rengage with the springs 282 and 285, at which instant the calling and called lines are avain restored in connection. The ringer or bel at the called sub-station having sounded the subscriber answers by removzn the receiver 405 from his switchhook 396. The said receiver is then connected inductively with the receiver 2 at the calling sub-station over circuits that will be lain exevhen the called subscriber permits his switch-hook to rise, the primary circuitsprings 406 and 407 then come into contact, as well as the springs 498, 409 and 410. t once a flow of current is established through the transmitter 411, which passes from ground Grs at the connector-side-switch-contact-point 264, side-switch-wiper 256, conl ductcrs 363 and 412, dierential-relaysprings 299 and 300, conductor 413, polechanging-relay 295, to the conductor 379, ringer-relay-springs 282 and 283, sideswitch-wiper 258, contact-point 270, couductor 388, rotary-line-Wiper 202, rotarynormal-conductor 362, rotary-line-conductor 390, 391, contact-point 392, conductor 393, sub-station relay-springs 414 and 415, conductor 416, springs 409 and 408, transmitter 411. primary winding 417 of the induction-coil 418, contact-point 419, spring 420, conductor 421, springs 406 and 407, conductor 398, contact-point 399, spring 400, to the vertical-lne-conductor 401, thence to the vertical-normal-conductor 361, vertical-line Wiper 201, conductor 402` contact-point 267. side-switch-wiper 25T, ringer-relaysprings 286 and 285, conductor 422, and through the retardation-coil 303 to the battery-lead 324,

and through battery B `to ground G. Included in this circuit is the pole-changing relay 295, which becomes energized, attracting, at once, its armature V294, the latter forcing the pole-changing-relay-spring 293 from engagement with thespring 297 and into engagement instead with the spring 296. As soon as the said springs (the springs 293 and 296) close together the transmitter 8 at the sub-station #320 is provided with current for talking purposes. This circuit extends from ground G's at the connector-sideswitch-contact-pcint 264, through sideswitch-wiper 256, conductors 363 and 412, pole-changing-relay-springs 296 and 293, conductor 356, ringer-relay-springs 289 and 28S, conductor 355, diiferential-relay-winding :291, conductor 354, rotary-line-relay 277, trunk-conductor 335, rotary-line-wiper 79, conductor 353, rotary-private-normal-relay 187,. conductor 352, contact-point 183, sideswitch-wiper 169, conductor 328, springs 91 and SH, rotary-line-conductor 327, spring 43, contact-point -1-1, conductor 380, sub-station relay-springs and 22, conductor 381, springs 31 and 30, transmitter S, primary winding 11 of the induction-coil 10, contactpoint 17, spring 16, primary circuit-springs 26 and 27, contact-point 45, spring 42, ver tical-line-conductor 321, side-switch-riper 168. contact-point 182, conductor 344, vertical-private-nornxal-relay 186, conductor 345, vertical-line-wiper 78, vertical-trunk-conductor vertical-line-relay 271, conductor 346, winding 292 of the dierential-relay 290, to the battery-lead 324 and through batterr B to ground G. Although the above energizing circuit includes the vertical and rotary line-relays 271 and 277 of the connector so that said relays are energized, and although, therefore, the trunkreleasesprings 275 and 276 are maintained in contact, the release-magnet 218 of the connector does not become energized because the differential-relay is not energized and because, therefore, the dierential-relay-springs 301 and 302 are kept apart. It is true that the same current that passes through the said line-relays also passes through the windings 291 and 292 of the differential-relay 290; but, as has been pointed out, v'hen the current pames through saidtwo differential-relay winding. 291 and 292, in the direction that it does under the present conditions, the two windings then neutralize or counteract each other, rendering the said relay inactive. e'ot only are the vertical and rotary line-relays 271 and :t7 of the connector maintained energized while the pole-changing-relay 295 is energized, but the vertical and rotary private-nonnal-relays of the first-selector are energized as well. When the first-selector side-switch passeslto third position andthe side-switch-wiper 167 engages the grounded contact-point 181 a potential is established at the private banks of the connectors of the group in which the normalconductors 423 and 424 ofthe line of the sub-station #120 terminate. This guarding potential is extended vto the said connectorprivate-banks over the private-normal-conductor 339; or when the private-normal-relays 186 and 187 are denergized, then such guarding potential is established through the private-normal-relay-springs 193 and 192; but when they are both energized, then the guarding potential is established through the private-normal-reiay-springs 191 and 190 instead. The transmitters 8 and 411 of the calling and called sub-stations being energized, as well as the primary windings l1 and 417 of the induction-coils 10 and 418, and the receivers at the respective sub-stations being connected in series with the secondary windings associated with the corresponding primary windings 11 and 417, it follows that the subscribers are then in a position to speak to each other.

The circuit'over which the voice-currents pass from one sub-station to the other is as follows: Beginning with the transmitter 411 at the called sub-station it extends through the primary winding 417, intact-point 419, spring 420, conductor 421, springs 406 and 407, conductor 398, contact-point 399, spring 400, vertical-line-conductor 401, verticalnormal-conductor 361, vertical-line-wiper 201, conductor-'102, contact-point 267, sides'witch-Wiper 257, ringer-'relay-springs 286 and 285, conductor 422,0ondenser 304-, trlmliconductor 334, vertical-line-wiper 78, conductor 345, vertical-private-normal-relay 186, conductor '344, contact-point 182, sideswitch-wiper 168, vertical-line-conductor 321, 42, contact-point 45, primary springs 27 and 26, spring 16, contact-point 17, primary winding 11 of the induction-coil 10, transmitter 8, springs 30 and 31, conductor 381, sub-station relay-springs 22 and 23, conductor 380, contact-point 44, spring 43, rotary-line-conductor 327, contact-point 92, spring 91, conductor 328, side-switchwiper 169, contact-point 183, conductor 352, rotary-private-normal-relay 187, conductor 353, rotary-line-wiper 79, rotary-trunk-conductor 335, condenser 305, conductor 379, ringer-relay-springs 282 and 283, sideswitch-wiper 258, contact-point 270, conductor 388, rotary-line-Wiper 202, rotarynormal-conductor 362, rotary-line-conductor 390, sprng 391, contact-point 392, conductor 393, sub-station relay-springs 414 and 415. conductor 416, springs 409 and 408, und again to the transmitter 111. While this connection is established the non-interfering characteristics of my system come into use if the subscriber at sub-station attempts to make a call. It should be evident thatfgif while the sub-stations #320 and #-130 are connected the subscriber at the substation .ii-230 should try to call, and thereby ground either or both of the line-conductors 390 and 401, he then will interfere with the conversation that is taking place between the connected sub-stations, since grounding the vertical-line-conductor 401 would short-circuit the pole-changing-relay 295, the transmitter 411, and the primary winding 417 of the induction-coil 41S. The short-circuit would, of course, extend from the ground G to the vertical-line-conductor 401, by whatever path the ground connection may be made at the interfering station. Clearly short-circuiting or shunting the polechanging-relay 295 would cause said relay to he denergized, of course, with the result that talking current for the calling subscriber is cut ot. The effect of shortcircuiting the transmitter 411 is obvious It is for the purpose of preventing such interference that l have provided'each sub-station with a non-interfering device like the one described at sub-station #320, comprising the line-relay-magnet 19 and the relaysprings 20, 21, 22 and 23. The connection described being established, should the subscriber at the sub-station #230 then remove his receiver 425 from its hook 426 the subnation relay 427 at said sub-station will be energized and its armature 42S locked to prevent a connection between the groundpost 429, the signaling-button-contact 430, or the ground-releasering 431 and the ground GS. The swi hook-springs 432 and 433, and 434 and 435 under the control of the cam-arms 437 and 436, respectively, are so adjusted that the springs 432 and 433, which are normally disengaged as indicated at sub-station #220, are thrown into contact as the switch-hook rises, after the subscriber removes his receiver, and before the spring 434 is separated from thek spring 435. At that time there is a dow of current through the sub-station relay 427 from the sub-station ground Grs through the conductor 438, springs 435 and 434, conductor 439, springs 432 and 433, sub-station relay 427, conductor 440, contact-point 441, spring-442, rotary-lineconductor spring 391, contact-point 392, conductor 393, sub-station relay-springs 414 and 415, conductor 416, springs 409 and 408, transmitter 411, primary 417 0f the induction-coil 41S, contact-point 419, spring 420, conductor 421, springs 406 and 407, conductor 398, contact-point 399, spring 400, vertical-line-conductor 401, verticalnormal-conductor 361, verticai-line-wiper 201, conductor 402, contact-point 267, sidesivitch-wiper 257, ringer-relay-springs 286 and 285, conductor 422, retardation-coil 303 to the battery-lead 324, and through battery B'to ground G. It will be noticed, therefore, that at the instant that the said substation rela}r 427 becomes energizedY the transmitter 411 receives current through two multiple circuits, one comprising the polechanging-relay 295 at the connector, and the other the sub-station relay 427, said circuits being grounded at Gr6 and G, respectively.

Another point should be noticed, namely that the releasing rod 443 that has supervision over the locking member 444 of the substation relay 427 is soadjusted that when the switch-hook rises to the point at which the said sub-station rela);Y is magnetized the said rod has risen suiciently to permit the said locking member 444 to operate. As soon as the relay 427 is magnetized the armature 428 is attracted by the pole-piece of said relay, which armature, as it strikes the polepiece, clears or disengages the locking member 444. The latter is forced upward in front of said amature to such a position that the armature is locked against the polepiece and retained there even after the energizing circuit is broken when the switchhook passes still farther upon its stroke. The said amature 428-, being depressed, causes the ring 445 to be separated from the spring thereby interrupting the continuity of the ground connection between the ground-post 429, the ground-contactpoint 430, and the release-spring 431 to the ground terminal G5, even after the groundcircuit-springs 447 and 448 are permitted to close. After this has been accomplished the subscriber at the sub-station .#230 may work his calling device, press his signaling-button, or hang up his receiver without interfering with the subscribers that are talking at the time. Since the substation #230 is connected in multiple with` the sub-station #130, the transmitter 449 is, therefore, energized in series with the sub-station relay 427 when the switch-hook-springs 434 and 435 separate and when the springs 450, 451 and 434 are brought into contact instead. The current passes from the ground G to the rotary-line-conductor 390, through the coil 427, springs 433 and 432, and 434, 451 and 450, transmitter 449, p Winding 453 to the vertical-line-conductor 401, and to the non-grounded terminal of battery B. It might appear that no voice-currents will pass to and from the line through the talking apparatus at station #230; but since the said sub-station relay 427 is brid by the condenser 452 the voice-currents d no trouble in passing. The object in this construction is to enable the subscriber at the interfering station to discover the fact that the line is busy at the time and to speak if he desires. Said voice-currents pass from the vertical-line-conductor 401, through the spring 455, contact-point 456, conductor 457, springs 458 and 459, conductor 460, spring 461, contact-point 462, primary winding 453 of the induction-coil 454, transmitter 449, springs 450, 451 and 434, conductor 439, springs 432 and 433, conductor 463, con- 

